Hydrocarbon production from shale formations is accomplished through natural formation fractures that are in communication with the producing wellbore. Stimulation treatments, such as hydraulic fracturing, are often performed on shale formation completions to enhance productivity. These stimulation treatments typically include surface active agents and other chemicals that interact with the formation and in situ formation fluids to enhance the flow and production of hydrocarbons.
In the past, core flow permeameters have been used to dynamically evaluate the interaction of oil and chemical treatments. For example, formation permeability to fluids has been measured by flowing brine, hydrocarbon or nitrogen representing different fluid phases through a whole solid core sample taken from a permeable formation such as sandstone. Different chemical treatments are applied to the formation core, and the resulting permeability measured and compared. However, permeameters are ineffective in evaluating core samples of impermeable oily shale. Static bottle tests have also been used to evaluate the interaction of oil and chemical treatments on formations but cannot distinguish between chemicals effective in aiding the production of hydrocarbons from chemicals that can slow hydrocarbon production by decreasing the interaction between the hydrocarbon, formation and natural formation brine. In such static tests hydrocarbon and chemical treatments are mixed, with or without shale or other formation material, and the resulting reaction of the oil is observed. Such static tests induce no fluid flow through the formation materials and therefore do not achieve the same accuracy as dynamic tests.
In the past, unconfined compressive strength (UCS) cells have been used to measure the strength of resin coated sand samples. A UCS cell includes a solid movable piston mounted within a cylinder that separates a test cell cavity from a closed pressure application cavity. A pressure port is provided on a first end of the cylinder to allow injection of pressurized fluid into the closed pressure cavity to cause the piston to move toward the test sample cavity and thus apply compressive stress to a resin coated sand sample that has been placed into the test sample cavity. A fluid outlet is provided on an opposing second end of the cylinder to allow fluids to exit from the test sample cavity while pressure is increased within the pressure cavity. The test cavity has no fluid inlet, and during typical resin coated sand testing operations, once the pressure cavity is pressured up the fluid outlet of the test cavity is closed off for the duration of the test.